Shaft mounted eddy current drive

ABSTRACT

A brushless shaft mounted eddy current drive has a coil mounted to bearings by way of a coil mount. The bearings are located on a hub. The coil mount is anchored to a fixed object. The pole pieces are coupled together by a nonmagnetic material to form a cavity that receives the coil. In another embodiment, a brushless drive has a coil rotatably mounted in a cavity within the pole pieces. A rotary inductive coil is mounted to the pole pieces about a stationary inductive coil. Alternating current is provided to the stationary coil to induce current into the rotary coil. In still another embodiment, an alternator is used to induce current into the rotating coil. In still a further embodiment, a brushless drive incorporates a liquid conductive rotatable coupler in the hub. In still another embodiment, the brushless drive energizes the coil in the electromagnet by way of bearings. The bearings are mounted onto a shaft that is coupled to the electromagnet. The shaft is located at one end of the drive, while a motor shaft is received by the opposite end of the drive.

This application is a continuation-in-part of U.S. application Ser. No.08/179,485, filed Jan. 7, 1994 now U.S. Pat. No. 5,446,327, whichapplication is a continuation-in-part of U.S. application Ser. No.08/056,132, filed Apr. 30, 1993 now U.S. Pat. No. 5,434,461, whichapplication is a continuation-in-part of U.S. application Ser. No.08/035,981 filed Mar. 18, 1993 now U.S. Pat. No. 5,465,018.

FIELD OF THE INVENTION

The present invention relates to variable speed drives that are mountedonto an output shaft of a motor, such as a fixed speed electric motor,and in particular the present invention relates to eddy current drives.

BACKGROUND OF THE INVENTION

There are many applications where it is desirable to have a fixed speedmotor provide a variable speed output. For example, in ventilationsystems, an ac synchronous motor is used to rotate an air mover, such asa fan. The energy efficiency of this system increases if the speed ofthe motor remains fixed while the speed delivered to the fan can bevaried.

In the prior art, there are variable speed drives that mount onto theoutput shaft of the motor. Around the outer circumference of the driveare one or more sheaves. The sheaves receive belts that are coupled to aload. The drive permits a controlled amount of slip. At zero slip, thefull rotary power of the motor output shaft is applied to rotate thesheaves. At full slip, the motor output shaft continues to rotate, butthe sheaves remain stationary under a load. Thus, at zero slip, the fullrotary power of the motor is applied to the load, while at full slip, norotary power is applied to the load.

In the prior art, there are eddy current drives. The amount of slip iscontrolled electrically using eddy currents. The output sheaves aremechanically coupled to poles of an electric coil. There are providedopposite, interdigitated poles. An armature provides a magnetic pathbetween the opposite poles. The armature is mechanically coupled to theoutput shaft of the electric motor. As the motor shaft rotates, thearmature also rotates at the same speed as the shaft. In order to rotatethe sheaves, current is applied to the coil. This creates anelectromagnetic coupling between the poles and the armature, wherein thearmature causes the poles and the associated sheaves to rotate. One suchprior art drive is disclosed in Albrecht et al., U.S. Pat. No.4,400,638.

It is desired to improve upon the prior art drives. The slip rings ofthe Albrecht et al. drive have the same diameter as, and are locatedadjacent to, the sheaves. One disadvantage of the slip ring arrangementis the wear on brushes. The chief complaint among customers who buy theprior an drives is brush wear. The brushes must be frequently replaced,adding to the maintenance cost of the drives. The larger thecircumference of the slip rings, the shorter the life of the brushesbecomes because for each revolution of the motor, the brushes are infrictional contact with a long length of the slip rings.

Another disadvantage of the slip ring arrangement of Albrecht et al. isthat as the drive is sized larger or smaller for respective larger orsmaller load applications, the circumference of the slip rings change.Thus, the slip rings must be custom made for each size drive. It isdesirable to make the slip rings a more uniform size, regardless of thesize of the drive, in order to manufacture and repair the drives moreefficiently.

Still another disadvantage of the slip ringarrangement of Albrecht etal. is the difficulty in protecting the slip rings and brushes from theenvironment. If the drive is used outside, it is subjected to moisture,which can reduce the life of the brushes.

A further disadvantage of the slip ring arrangement of Albrecht et al.is that brushes are required to provide current to the rotating coil. Asnoted above, brushes are subject to wear and must be frequentlyreplaced. It is desirable to provide a means of supplying current to thecoil less subject to wear and requiring less maintenance than brushes.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a shaft mounted eddycurrent drive that has prolonged brash life.

Another object of the present invention is to provide a drive designthat uses the same size slip rings regardless of the power requirementsof the drive.

Still another object of the present invention is to provide a brashlessdrive.

The drive of the present invention includes a hub that is structured andarranged to be coupled to a motor shaft. The hub has a shoulder, whichshoulder is coupled to the hub. An electromagnet is mounted on the huband abuts against the shoulder. The electromagnet is rotatably coupledto the hub. There is a driven member that is mounted to the hub bybearings. The driven member has a load portion and an armature, with theload portion being structured and arranged to be rotatably coupled to aload and the armature being located adjacent to the electromagnet.

The drive of the present invention has several advantages over prior artdrives. One advantage is due to the design of the slip rings. The sliprings are located at the outer end of the drive and are of relativelysmall diameter. In the preferred embodiment, a slip ring shaft providesa support for mounting the slip rings. The small diameter of the sliprings greatly prolongs brush life by presenting a relatively smallcircumference that the brushes must traverse for each revolution of theslip rings. Because the brushes contact shorter lengths of slip ringsper revolution, the lives of the brushes are prolonged.

Also, by providing the slip rings on a separate slip ring shaft, thesize of the slip rings is independent of the sizes of the motor shaft,the sheave and the drive in general. Thus, as the design of the drive isenlarged to provide a drive with more horsepower, or reduced to providea drive with less horsepower, the size of the slip rings, and thus thebrush holders, can remain the same. This uniformity in size of sliprings, which is independent of the size of the drive, reducesmanufacturing costs while allowing flexibility in producing a productline of plural drives, each of which is designed for a specifichorsepower. Inventory costs are reduced as well, because bothmanufacturer and user need only stock one size of slip rings and brushholders.

The drive also provides a housing or cover for containing and protectingthe slip rings and brushes from the elements. This is important fordrives that are used outside, as brush life is extended. The coverprevents moisture from contacting the brushes and the slip rings.

The design of the drive allows for easy partial disassembly whilemaintaining the connection of the drive to the load and to the motorshaft. The brush holders, slip rings, fan and electromagnet can beremoved while leaving the hub connected to the motor shaft and thesheaves coupled to the load. This reduces maintenance time because thedrive does not have to be completely removed during disassembly.

The drive is more stable in operation because the sheaves are fullymounted on bearings and are located closer to the end of the hub thatcouples to the end of the motor. Prior art drives mount the brush holderbracket on the same end of the hub as the sheaves. This causes thesheaves to either be mounted further from the motor (which unfavorablyloads the motor shaft and produces vibration) or to be only partiallymounted onto a bearing (which produces unbalancing and vibration of thesheaves). The drive of the present invention does not suffer these priorart problems because the sheaves are fully supported by the bearings. Inaddition, the sheaves, as well as the bulk of the mass of the driver,are located closer to the motor than the prior art drives. Thisdrastically reduces the overhung load on the motor shaft, prolongingmotor life.

Another advantage of the drive of the present invention is that thesheaves are fully exposed at all times. In the prior art, the brushholder bracket extends across the sheaves. With the drive of the presentinvention, the slip rings and brush holder bracket are located on theopposite end of the drive from the sheaves. Thus, the belts can beinstalled onto and removed from the sheaves without removing the brushholder bracket. In addition, a conduit is used to prevent rotation ofthe brush holder bracket. The conduit is anchored to the motor andextends through the belts. This arrangement allows the belts to beinstalled and removed without disassembling any part of the drive.

Still another advantage of the drive is the coupling of theelectromagnet to the hub and the fan to the electromagnet. The motorshaft rotates the hub, the electromagnet and the fan continuously atmotor speed. This continuous movement of the electromagnet and the fanproduces continuous cooling of the electromagnet. Prior art driveslocate the electromagnet on the driven member, which may be stationaryor operating at a low speed. The electromagnet on prior art drives isnot cooled as effectively as with the present invention due to thereduced rotational speed. Effective cooling of the electromagnetprolongs the life of the electromagnet.

A brushless variable speed drive is also provided. The drive has arotatable member that is structured and arranged to be rotated by amotor. There are pole pieces that have plural interdigitated poles, withthe poles being separated from an armature by a gap. One of either ofthe pole pieces of the armature is fixedly coupled to the rotatablemember. The pole pieces have a cavity therein. There is a coil locatedwithin the cavity and coupled to a beating located on the rotatablemember. The coil is coupled to the beating by a coil mount which has aportion that is magnetic located adjacent to the coil.

In another aspect of the present invention, a variable speed brushlessdrive includes a rotatable member that is structured and arranged to berotated by a motor, a pole piece assembly having a first pole piece anda second pole piece, each of which has poles that are separated from anarmature by a gap, with the first pole piece being coupled to therotatable member and the second pole piece being coupled to the firstpole piece by a retaining member. The retaining member is made of anonmagnetic material.

In another aspect of the present invention, a variable speed brushlessdrive is provided. Electrical power is provided to the drive coil so asto produce a magnetic field by the pole pieces, by way of ac inductivecoupling. A stationary coil is provided, which coil is connected to apower supply. A rotating coil is provided, which coil is coupled to thepole piece assembly in the drive. A magnetically susceptible pathconnects the stationary coil and the rotating coil together. Thestationary coil is provided with alternating current, whereinalternating current is induced into the rotating coil. The inducedalternating current is rectified by a bridge rectifier to directcurrent. The direct current is provided to the drive coil and the polepieces.

In still another aspect of the present invention, an alternator typebrushless drive is provided. The drive has a rotating coil that iscoupled to the drive coil and pole piece assembly. A stationary coil isfixed to a stationary platform. The stationary coil is enclosed in asecond set of pole pieces. Direct current is provided to the stationarycoil, wherein the second set of pole pieces generate a magnetic field.This magnetic field that is generated by the second set of pole piecesinduces an alternating current into the rotating coil. The alternatingcurrent is rectified to direct current, which direct current is providedto the drive coil in order to drive the armature.

In still another aspect of the present invention, a liquid conductorcoupler is mounted in-line with the axis of rotation of the drive.Direct current is provided to the drive coil through the liquidconductor coupler.

In still another aspect of the present invention, a variable speed driveis provided with a speed sensor coupled to a rotating member of thedrive. The drive has a first member with pole pieces and a coil and asecond member with an armature. The speed sensor is coupled to one ofthe first or second members. The other of the first and second membershas a periodically changing pattern which is sensible by the speedsensor. A signal transmitter is located on the one member and isconnected to the speed sensor. A signal receiver is located on a thirdmember so as to receive a signal produced by the signal transmitter. Thethird member is stationary with respect to the rotation of the first andsecond members.

In still another aspect of the present invention, the rotating coil inthe electromagnet is provided with current directly through at least onebeating. The beating has first and second portions, with the firstportion being electrically connected to the drive coil, the secondportion being electrically connected to a stationary wire and the firstand second portions being electrically connected together.

By using bearings to energize a drive coil, the need for brushes iseliminated. In addition, to providing a power coupling, the bearing canprovide structural support to a speed sensor.

The bearings are mounted to a shaft that is located at one end of thehub. The other end of the hub receives the motor shaft. Thus, thebearings can be sized small because they need not receive the motorshaft. In addition, the shaft can be an output shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional side view of the shaft mounted eddycurrent drive of the present invention, in accordance with a preferredembodiment.

FIG. 2 is a view showing the outer end of the drive, with a housingaround the slip rings and brush holder partially cut away.

FIGS. 3 and 5 are side views showing the interiors of the first andsecond portions, respectively, of a brush holder, in accordance with apreferred embodiment.

FIG. 4 is an end view showing how the first and second portions of thebrush holder fit together.

FIG. 6 is a top plan view of the brush holders.

FIG. 7 is a cross-sectional view taken along lines VII--VII of FIG. 6.

FIG. 8 is a side view of the first portion of a brush holder, with abrush installed, and the second portion removed for clarity.

FIG. 9 is a partial cross-sectional side view of the drive of thepresent invention, in accordance with another embodiment showing abrushless design.

FIG. 10 is a view showing the outer end of the drive of FIG. 9.

FIG. 11 is a partial cross-sectional side view of the drive of thepresent invention, in accordance with a further embodiment showing arotary transformer for providing current to the rotating coil.

FIG. 12 is a view showing the outer end of the drive of FIG. 11.

FIG. 13 is a partial cross-sectional side view of the drive of thepresent invention, in accordance with a still further embodiment showingan alternator for providing current to the rotating coil.

FIG. 14 is a partial cross-sectional side view of the drive of thepresent invention, in accordance with a still further embodiment showinga liquid filled rotary slip ring for providing current to the rotatingcoil.

FIG. 15 is a partial cross-sectional side view of the liquid filled slipring used in the embodiment of the drive of FIG. 14.

FIG. 16 is a cross-sectional side view of the drive of FIG. 11illustrating another embodiment of the input/output mechanisms of thedrive.

FIG. 17 is a cross-sectional side view of the drive of FIG. 11illustrating a further embodiment of the input/output mechanisms of thedrive.

FIG. 18 is a cross-sectional side view of the drive of FIG. 11illustrating a still further embodiment of the input/output mechanismsof the drive.

FIG. 19 is a cross-sectional side view of the drive of FIG. 11illustrating a still further embodiment of the input/output mechanismsof the drive.

FIG. 20 is a partial cross-sectional side view of a drive, in accordancewith another embodiment, showing a speed sensor mounted on a rotatingpart.

FIG. 21 is an electrical schematic diagram of the speed sensorarrangement of FIG. 20.

FIG. 22 is an electrical schematic diagram of another embodiment of thespeed sensor arrangement of FIG. 20.

FIG. 23 is an electrical schematic of a bridge rectifier used inconjunction with the drives of FIGS. 11 and 13.

FIG. 24 is a partial cross-sectional side view of the drive of thepresent invention, in accordance with a further embodiment showing abearing power coupling for providing current to the rotating coil.

FIG. 25 is a close up cross-sectional view of a portion of the bearingpower coupling of FIG. 24.

FIG. 26 is a view showing the outer end of the drive of FIG. 24.

FIG. 27 is a partial cross-sectional close up view of the drive, showinganother embodiment of the bearing power coupling.

FIG. 28 is a partial cross-sectional view of the drive, showing stillanother embodiment of bearing power coupling.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, there is shown a partial cross-sectional side view of thedrive 11 of the present invention, in accordance with a preferredembodiment. The drive 11 has a shaft mounted portion and a load portion.The shaft mounted portion includes a hub 13, pole pieces 15 and a coil17. The shaft mounted portion mounts onto the shaft of a motor and isrotated directly by the motor shaft. The load portion is rotated by anelectromagnetic field developed by the shaft mounted portion. The loadportion is coupled to the load (e.g. a fan) and includes an armature 19and sheaves 21. In addition, the drive includes slip rings 23, a brushholder bracket 25 and brush holders 27.

The shaft mounted portion will now be described. The hub 13 is generallyin the form of a sleeve. The hub 13 has a cylindrical cavity 29 locatedtherein for receiving a shaft 31 of a motor 33. The hub 13 is coupled tothe shaft 31 by a conventional and commercially available compressiontype shrink disk (not shown). Alternatively, the cavity 29 may be keyedor threaded to receive respective keys or threads on the motor shaft.The hub 13 has an outer end portion and an inner end portion (with innerbeing referenced as closer to the motor and outer being referenced asfurther from the motor 33).

Mounted on the outer end portion of the hub are the pole pieces 15.There are two pole pieces, an inner piece and an outer piece. Each polepiece 15 is made up of an annular portion 35, with poles 37 extendingfrom the outer diameter of the annular portion and a lip 39 extendingfrom the inner diameter of the annular portion. The poles 37 on anindividual pole piece are spaced apart by gaps. When the pole pieces areassembled as shown, the poles from the inner and outer pole pieces areinterdigitated so as to form alternating polarities around thecircumference of the assembly of pole pieces. The assembled pole pieces15 encircle the coil 17 of wire. Thus, the coil 17 is encircled by theannular portions 35, lips 39 and poles 37 of the pole pieces. The polepieces and the coil extend around the circumference of the hub. The polepieces 15, and thus the encircled coils, are secured to the hub 13 bybolts 41. The hub 13 has a circumferential shoulder 43 that extendsradially outward to receive the bolts and to position the pole pieces15. The pole pieces abut against the shoulder 43. The pole pieces aremade from a low carbon steel, which is magnetic, so as to provide a pathfor a magnetic field.

The load portion will now be described. The sheaves 21 are mounted tothe hub 13 by way of bearings 45. In the preferred embodiment, thebearing 45 is a double row ball bearing. Alternatively, the bearing maybe two bearings. The bearings 45 are located on the hub between theshoulder 43 and a snap ring 47 that is on the hub. The bearings 45extend around the circumference of the hub. The sheaves 21 are locatedaround the outer circumference of the bearings. The sheaves 21 arepositioned on the bearings by a shoulder 49 on one end and bolts 51 onthe other end. The sheaves receive belts 22, which are rotatably coupledto a load such as a fan.

The armature 19 is coupled to the sheaves by a radially extending wall53. The armature 19 is a hollow cylinder and is made of a material thatis high in conductivity and permeability. The wall has openings 55therethrough that communicate with a cavity 56 formed by the armature 19and the wall 53. The cavity 56 receives the pole pieces 15. The openings55 allow air circulation through the pole pieces. The sheaves 21,armature 19 and wall 53 form an integral assembly. Alternatively, aninterior sleeve can be press fit into the inside diameter of thearmature. The interior sleeve can be made of a material that is suitablefor the production of eddy currents (high conductivity, highpermeability) while the armature around the sleeve can be designed todissipate heat.

The slip rings 23 are secured to the pole pieces 15 by way of a fan 57.The fan 57 is located so that the pole pieces 15 are interposed betweenthe fan 57 and the sheaves 21. Bolts 59 secure the fan 57 to the outerpole piece 15. The fan has openings 61 therein so that as the polepieces rotate, the fan causes air to circulate through the openings 55,61 and the pole pieces for cooling.

A slip ring shaft 63 is coupled to the fan 57 by bolts 65. The slip ringshaft 63 extends in an axial direction away from the sheaves 21. Theslip ring shaft has first and second outer surfaces 67, 69. The firstouter surface 67 is located at the outer end of the slip ring shaft. Theslip rings 23 are mounted on the first surface 67 with a key 71 and anend plate 73. The end plate 73 is bolted onto the outer end of the slipring shaft. The slip rings 23 extend around the circumference of theslip ring shape. Wires 75 connect the slip rings 23 to the coil 17. Thewires 75 extend through passageways 76 drilled or otherwise formed inthe slip ring shaft 63 and the fan 57.

The brush holder bracket 25 has a sleeve portion 77 that is mountedaround the second surface 69 of the slip ring shaft 63 by way of abearing 79. The beating 79 is secured in place against a shoulder on thefan 57 and snap rings. The bracket 25 has a radial extension portion 81that extends past the armature 19.

The brush holders 27 are coupled to the radial extension portion 81 ofthe brush holder bracket 25. Referring to FIGS. 3-8, there are two brushholders 27, one for each brush 85. Each brush holder 27 has a firstportion 82 (shown in FIG. 3) and a second portion 83 (shown in FIG. 5).The first portion 82 is provided with pins 84 on its interior surface,while the second portion 83 is provided with holes 86 for receiving thepins 84. The two portions 82, 83 snap fit together with the pins 84inserted into the holes 86 (see FIG. 4). Each portion has a groovelocated therein. When the portions are assembled, the groove forms agenerally rectangularly shaped cavity 87 for receiving the carbonbrushes 85 (see FIGS. 6 and 8). Each side wall of the cavity 87 has ashallow groove 88 that allows the brushes to move inside the cavity.

Each brush 85 is connected to a contact 94 by a flexible wire 92. Aspring 89 is interposed between the brush 85 and the contact 94. Thecontact 94 has edges that bear on a top surface 94A of the assembledbrush holder 27. Thus, the brush 85 is prevented from being pulled outfrom the bottom 94B of the brush holder. A clip 91 overlies the contact94. The clip is L-shaped to provide a connection point for a wire 91A.The wires 91A connected to the clips are routed to an external powersource by a conduit 93. The clip 91 is secured to the brush holder by ascrew 92A. The clip is located inside of a recess 91B on the top of thebrush holder. This recess 91B locates the clip 91, and the connectionpoint with the wire 91A entirely within the protective confines of thebrush holder. The contact 94 makes electrical contact with the clip 91.

The two brush holders 27 are oriented with respect to each other asshown in FIG. 6, so that the clips, when installed, face oppositedirections. This simplifies the wire connections with the clips. Thebrush holders are bolted to the brush holder bracket by bolts that arereceived by holes 95. Referring to FIG. 2, the brush holders 27 arelocated close to the slip rings 23 so that the brushes 85, whichprotrude out of the cavities, can contact the slip rings.

The brush holder bracket 25 has end walls 97 that extend in an axialdirection. The end walls receive a housing 99 or cover, a portion ofwhich has been broken away in FIGS. 1 and 2 to more clearly illustratethe slip rings and brush holders. The housing 99 and the bracket 25completely encase the slip rings 23 and the brush holders 27 so as toprotect the slip rings and brush holders from the environment andmoisture, thereby extending the life of the brushes. Screws are used tocouple the housing to the bracket 25. The housing is removable to allowaccess to the slip rings and brush holders.

The brush holder bracket 25 has an extension 101 (see FIG. 1) that isused to position a speed sensor 103 adjacent to the rotating armature.The outer surface of the armature 19 is scored at regular intervals (seeFIG. 2). In the preferred embodiment, the scoring takes the form ofgrooves 105 which form peaks 107. The sensor 103 is a magnetic pulsepickup. Thus, as the steel armature 19 rotates, every peak 107 iscounted. Conventional control circuitry, not shown, is used to monitorthe signal produced by the sensor and to control the amount of currentsupplied to the brush in order to control the speed of the armaturerotation.

The drive need not be supplied with a speed sensor. Many applicationsalready have control systems. For example, in HVAC, inputs oftemperature and pressure are used to control the speed of the armaturerotation.

The assembly of the drive will now be described, referring to FIG. 1.The bearings 45 are installed and secured onto the hub 13. Then, thearmature and sheave assembly 19, 21 are installed and secured onto thebearings 45. The pole pieces 15 and coil 17 are assembled together tomake up an annular electromagnet. The pole pieces 15 and coil 17 areinstalled onto the hub 13 with the pole pieces in abutting relationshipwith the shoulder 43. The pole pieces are then bolted 41 in place. Thefan 57 and the slip ring shaft 63 are bolted 65 together. The fanassembly is bolted 59 to the pole pieces. The center 111 of the fan isdisk shaped and received by the hub cavity 29 to center the fan withrespect to the pole pieces. The support bracket 25 is then mounted, byway of bearings 79, to the slip ring shaft. Then, the brush holders 27and speed sensor 103 are coupled to the bracket 25.

The drive 11 is then installed onto a motor shaft 31. The motor shaft 31is inserted into the hub cavity 29 and a compression disk is used tofirmly secure the hub to the shaft. The cover 99 is installed onto thebracket 25.

The conduit 93, which contains the wires connected to the brushes, isanchored to a fixed platform, such as the motor 33. A bracket 33A isused to couple the conduit 93 to the motor 33. The wires from the speedsensor 103 are typically tie wrapped to the outside of the conduit 93.

In the preferred embodiment, the conduit 93 is positioned between thesheaves 21 and the load. Thus, when the belts are installed on thesheaves, the conduit 93 extends through the loops formed by the belts;that is the belts 22 extend around both the sheaves 21 and the conduit93. This arrangement of the conduit 93 through the belts 22, togetherwith the arrangement of the slip rings and the bracket on the outer endof the drive, away from the sheaves, allows the belts to be installedand removed from the sheaves and the load, without disconnecting theconduit and without removing the bracket 25 and the brush holders 27.Thus, the belts can be quickly installed or removed without disturbingthe drive, thereby reducing maintenance and down times.

The sheaves 21 are fully supported by the bearings 45, thereby providinglong operational life of the sheaves and bearings 45. In addition, thesheaves and the bulk of the mass (the electromagnet) are located closeto the motor 33. This arrangement reduces the overhung load on the motorshaft.

The operation of the drive 11 will now be described. The motor 33 isstarted and the shaft 31 is rotated. As the shaft rotates, it rotatesthe pole pieces 15 and the coil 17. The sheaves 21 do not rotate, asthey are held stationary by the load.

To rotate the sheaves, a selected amount of current is provided to thecoil, by way of the brushes and slip rings. This energizes the coil,which causes an electromagnetic field to be developed between adjacentpoles. The armature becomes electromagnetically coupled to the polepieces, wherein the armature and the sheaves are rotated. If theelectromagnetic field is weak, then there will be some slip between thearmature and the pole pieces. Thus, for every revolution of the polepieces, the armature will rotate less than one revolution. Bycontrolling the strength of the energizing current to the coil, theamount of slippage and the speed of the armature can be controlled.

The drive 11 may be partially disassembled for maintenance andinspection purposes without uncoupling the drive from the load. Thus,the belts may be retained on the sheaves 21 during partial disassembly.To partially disassemble the drive 11, the bolts 59 are removed, therebyallowing the fan 57, slip ring shaft 63 and bracket 25 to be removedfrom the pole pieces 15. Then, the bolts 41 are removed, therebyallowing the pole pieces 15 and coil 17 to be removed from the interiorcavity 56 of the armature 19. The electromagnet (the pole pieces and thecoil) and the slip ring arrangement can be worked on and thenreinstalled. During the partial disassembly of the drive, the hub 13 andarmature-sheave assembly 19, 21 remain coupled to the motor shaft and tothe load. Thus, the design of the drive simplifies maintenance andinspection procedures.

Replacing the brushes 85 is also simple. One method involves removingthe clip 91 (see FIG. 8). The contact 94 and brush 85 are then removedand replaced, and the clip 91 is reinstalled. Thus, the brush holders 27remain coupled to the bracket 25. Another method of changing the brushesinvolves removing and disassembling the brush holders 27 into theirfirst and second portions 82, 83. This procedure allows the brushholders to be cleaned of carbon dust. After cleaning, the brush holdersare reassembled and new brushes are installed.

Replacement of the slip rings 23 is also simplified, requiring onlyremoval of the end plate 73, slipping the slip rings off of the shaft 63and reinstailing a new pair. Replacement of the brushes and slip ringscan be performed while leaving the drive intact on the motor shaft 31.

In FIGS. 9 and 10, there is shown the drive 111 of the presentinvention, in accordance with another embodiment. Like numbers in thefigures designate similar parts and components. The embodiment of FIGS.9 and 10 is referred to as a brushless drive, because brushes are notused. Instead, the coil 17 is held in a non-rotating manner relative tothe pole pieces 113, 115 and the armature 119. Because the coil 17 isfixed, no slip rings or brushes are required to provide electric currentto the coil. Instead, the coil is wired directly to a source of electricpower (or to a control circuit regulating the amount of power suppliedto the coil).

The hub 117 of the drive 111 has an outer end portion that extends outbeyond the pole pieces 113, 115.

The pole pieces have two components, namely an inner pole piece 113 andan outer pole piece 115. The inner pole piece 113 is, referring to theorientation of FIG. 9, shaped like a backwards "C". It has individualpoles 119A which are interdigitated with the poles on the outer polepiece 115. The inner pole piece 113 has a mounting portion 121 thatcontacts the hub 117. The mounting portion is secured to the hub by thebolts 41. The outer pole piece 115 is a single piece having an annularportion 122 and plural poles 119 extending from the annular portion.

The outer pole piece 115 is coupled to the inner pole piece 113 by aretaining ring 123 that is nonmagnetic and low in magnetic permeability.Thus, the retaining ring123 does not detract from the magnetic fieldcoupling between the poles and the armature. For example, the ring 123could be copper or stainless steel. Furthermore, the retaining ring123is located along the inside diameter of the poles 119 so as to notinterfere with the magnetic field between the poles and the armature.The inner circumference of each pole 119 is chamfered so as to form apoint at the end of each pole. This chamfering forms an upside down "V"cavity as shown in FIG. 1. In the preferred embodiment, the retainingring 123 is located within this cavity. The retaining ring123 is securedto the pole pieces 113, 115, such as by welding, so as to make a singlepole piece assembly. The fan 57 is bolted to the annular portion of theouter pole piece 115.

Together, the pole piece assembly forms a cavity 125. The coil 17 islocated within the pole piece assembly cavity 125. The annular coil 17is supported within the annular cavity 125 by a coil mount 127. The coilmount 127 has a lip 129 for supporting the coil. The coil can be securedto the coil mount by a suitable adhesive. The coil mount 127 issupported on the hub 117 by bearings 131. The coil mount 127 thusextends from a position outside of the pole pieces to a location insideof the pole piece cavity 125. A snap ring133 and a step 134 are used toretain the coil mount 127 to the bearings 131. The coil 17 and the coilmount 127 are separated from the pole pieces 113, 115 by a gap 135. Thecoil 17 remains stationary while the pole pieces 113, 115 rotaterelative to the coil. The coil mount 127 is made of the same material asthe pole pieces 113, 115, so as to provide a path for a magnetic fieldabout the coil.

The bearings 131 are located on the outer end of the hub 117. Thebearings 131 supporting the coil mount 127 are set off from the innerpole piece 113 by a spacer ring 137. A snap ring 139 retains thebearings 131 on the hub 117.

A bracket 141 is bolted onto the coil mount 127. The bracket 141 isshaped like an upside down "L" (referring to the orientation of FIG. 9).The speed sensor 103 is mounted to the extension portion 101 of thebracket 141. The outside diameter of the armature 19 has grooves 105 andpeaks 107 to form teeth (see FIG. 10), which teeth are detected by thespeed sensor during the rotation of the armature. The teeth extendaround the entire circumference of the armature. (In FIG. 10, only a fewteeth are shown.) A conduit 93 is coupled to the bracket. The conduit 93contains the wires 143 for energizing the coil with current. The conduit93 is anchored to a fixed platform, such as the motor. This anchoringprevents rotation of the coil 17 and the speed sensor.

In operation, the hub 117 rotates the pole pieces 113, 115 at the samespeed as the motor shaft 31. The coil 17 does not rotate, as it is heldstationary by the anchored or fixed bracket. Because the coil does notrotate, no brushes are required to provide current to the coil.

When no current is applied to the coil, there is no magnetic couplingbetween the pole pieces and the armature. Therefore, under a load, thesheaves 21 and the armature 19 do not rotate. Application of current tothe coil provides magnetic coupling between the pole pieces and thearmature, causing the armature and the sheaves to rotate. The coilremains stationary irregardless of the rotation of the pole pieces orthe armature.

Because the drive 111 of FIGS. 9 and 10 does not use brushes, lessmaintenance is required than with drives that do require brushes.

The brushless drive 111 of FIGS. 9 and 10 can easily be assembled anddisassembled in the field. This is a desirable characteristic,particularly if a drive picks up dirt or debris and must be cleaned. Todisassemble the drive, the snap ring 139 is removed from the hub 117.Then, the beating 131, the coil mount 127 and the coil 17 are removedfrom the hub and the pole pieces. The pole piece assembly can be removedby unscrewing the bolts 41. The armature can be removed by removing thesnap ring47. To reassemble the drive, the armature 19 and its beatingare reinstalled into the hub. The pole pieces 113, 115 are bolted inplace onto the hub. Then, the coil mount 127 is coupled to the beating131. The bearing 131 is installed onto the hub 117 and the coil 17 islocated within the cavity 125.

Although the coil mount 127 has been described as a single piece, it maybe made of plural pieces. Because the portion of the coil mount outsideof the pole piece cavity 125 does not contribute to the magnetic fieldpath around the coil, there is no need for this portion of the coilmount to be magnetic. For example, the coil mount could be made of amagnetic inner piece and a nonmagnetic outer piece. The magnetic innerpiece would be located between the outer pole piece 115 and the mountingportion 121 of the inner pole piece 113 and would be adjacent to thecoil. This inner piece would maintain a magnetic path around the coil17. The nonmagnetic outer piece would couple the magnetic inner pieceand the coil to the beating 131. The inner and outer pieces could bejoined together by bolts.

In FIGS. 11 and 12 there is shown a drive 211 of the present invention,in accordance with a further embodiment. The drive 211 incorporates anac inductive rotative power coupling instead of brushes in order toprovide electrical current to the rotating coil 17. Like numbers in thefigures designate similar pans and components.

The embodiment of FIGS. 11 and 12 is a brushless drive in which the polepieces 15 and the drive coil 17 rotate relative to tile armature 19. (Inthe embodiments of FIGS. 11-13, the coil 17 will be referred to as adrive coil to distinguish it from the power coupling coils.) The drive211 of FIG. 11 combines the relatively continuous pole pieces 15 of thedrive 11 of FIG. 1 with a brushless design. Use of a relativelycontinuous pole pieces minimizes gaps in the pole pieces which reducethe overall efficiency of the drive.

In order to connect the rotating coil 17 to a source of electric poweror a control circuit regulating the amount of power supplied to the coil17, a pair of inductively coupled coils 217 and 219 are used. One coil217 is mounted stationary relative to the rotating coil 17 and the polepieces 15. The electrical power source or control circuit is wireddirectly to the stationary coil 217. The second coil 219 is rotatablymounted adjacent to the stationary coil 217 and rotates in unison withthe coil 17 and the pole pieces 15. The rotating coil 219 is wired viathe bridge rectifier to the coil 17. Current applied to the stationarycoil 217 by the power source induces a current in the rotating coil 219which is supplied to the coil 17.

The structure of the ac inductive rotative power coupling drive 211 willnow be described. The structure of the load portion of the drive 211including the sheaves 21, the bearings 45 and the armature 19 isidentical to the load portion of the drive 11 which is described above.

The rotating coil 219 is coupled to an inner section 225 which in turnis coupled to the fan 57 with bolts 221. A first portion 225A of theinner section extends outward from the pole pieces 15 and has an insidediameter slightly larger than the outside diameter of the hub 13. Thefirst portion 225A is a hollow robe. Adjacent the pole pieces 15, asecond portion 225B of the inner section extends radially outward fromthe first portion 225A to the fan 57. The rotating coil 219 is coupledto the first portion 225A of the inner section so as to abut the secondportion 225B. The coil 219, which is annular in shape, can be coupled tothe first portion 225A by adhesive bonding. The inner section also has athird portion 225C, which is "L" shaped in cross-section. The thirdportion extends from the outer circumferential end of the second portion225B in a direction that is parallel to the first portion 225A. Thus,the third portion 225C also forms a hollow robe. The inner portion 225is bolted to the fan by bolts 221, which extend through the thirdportion 225C.

A bridge rectifier 229 is coupled (by adhesive bonding) to the secondportion 225B of the inner section adjacent to the rotating coil 219. Thebridge rectifier 229 is electrically connected between the rotating coil219 and the coil 17. The bridge rectifier 229 provides direct current tothe coil 17 from an alternating current induced in the rotating coil 219by an ac electrical power source. The bridge rectifier is electricallyconnected to the rotating coil 219 with wires 231. Wires 233 extendthrough the fan 57 and electrically connect the bridge rectifier 229 andthe coil 17.

The stationary coil 217 is mounted to and supported by a coil mount 235which remains stationary relative to the coil 17 and the rotating coil219. The coil mount 235 is supported on the first portion 225A of theinner section by bearings 237 located about the outside diameter of thefirst portion 225A. The bearings 237 are held in place on the firstportion 225A by a shoulder 239 of the coil mount 235, a shoulder of thefirst portion 225A, and snap rings 241 and 243. The shoulder 239 isseparated from the first portion 225A by a gap 240.

The coil mount 235 extends radially outward from the bearings 237. Thecoil mount 235 forms a lip 245 at the outer radial edge of the coilmount 235. The lip 245 extends towards the pole pieces 15 adjacent to aninside diameter of the third portion 225C. The lip 245 is separated fromthe third portion 225C by a gap 247. The stationary coil 217 is securedwith a suitable adhesive to the inside diameter of the lip 245 of thecoil mount 235 facing the rotating coil 219.

The coil mount 235, lip 245, and first and second portions 225A and 225Bof the inner section 225 form a cavity 249 across which the coils 217and 219 are opposed. The coil mount 235 and the inner section are formedof magnetic susceptible materials in order to maintain a magnetic pathabout the coils 217 and 219. The coil mount 235 and the inner section225 can be formed of iron, magnetically susceptible low carbon steel,amorphous silicon steel, or powdered ferrite core material.

A junction box 251 is secured to a flattened portion of the outsidediameter of the coil mount 235. Referring to FIG. 12, a conduit 253couples the junction box 251 to a fixed platform (such as the motor 33or the ground), in order to prevent rotation of the coil mount 235.Similar coupling to prevent rotation is shown in FIG. 1. Wires extendfrom the junction box 251 through the coil mount 235 to the stationarycoil 217 to electrically connect the stationary coil 217 to the powersource. The junction box 251 is fastened to the coil mount 235 withscrews (not shown).

A bracket 255 is coupled to the conduit 251. The bracket 255 is shapedlike an upside down "L" (referring to the orientation as shown in FIG.11). The bracket 255 is oriented to extend over the armature 19. Thespeed sensor 103 is mounted to an extension portion 101 of the bracket255 in a position to detect movement of the teeth formed by the grooves105 and peaks 107 of the armature 19 (see FIG. 12).

In operation, the hub 13 rotates the pole pieces 15 at the same speed asthe motor shaft 31. The coil 17 is rotated with the pole pieces 15.

In order to provide electrical current to the coil 17, alternatingcurrent is applied to the stationary coil 217. The alternating currentmay be varied, for example, between a potential of 0 to 120 volts, andmay be various wave types including sinusodial, square wave, andtriangular. In addition, the alternating current need not be at 60 Hz,but can be other frequencies.

When no current is applied to the stationary coil 217 there is nocurrent induced in the rotating coil 219 and thus no current is providedto the coil 17. Therefore, there is no magnetic coupling between thepole pieces 15 and the armature 19. Under a load the sheaves 21 and thearmature 19 do not rotate if there is no magnetic coupling between thearmature 19 and the pole pieces 15.

When alternating current is applied to the stationary coil 217, currentis induced in the rotating coil 219 through the coil mount 235 and theinner piece 225. A magnetic path is formed between the coils 217, 219 byway of (going in a counterclockwise direction in FIG. 11 ) the coilmount 235, the shoulder 239, the gap 240, the first portion 225A, thesecond portion 225B, the third portion 225C, the gap 247 and the lip245. The bridge rectifier 229 transforms alternating current supplied bythe rotary coil 219 to direct current which is supplied to the coil 17.The current in the coil 17 causes the pole pieces 15 and the armature 19to become magnetically coupled, thereby rotating the armature 19 and thesheaves 21. Increasing the voltage (or power) to the stationary coil 217increases the magnetic coupling between the pole pieces 15 and thearmature 19, thereby increasing the rate of rotation of the armature 19.

Because the drive 211 of FIGS. 11 and 12 does not use brushes, lessmaintenance is required than with drives that do use brushes.Furthermore, because no gap is required between the coil 17 and the polepieces 15 the drive 211 is more efficient than drives which require agap between the coil and pole pieces.

In FIG. 13 there is shown a drive 311 of the present invention, inaccordance with a still further embodiment. The drive 311 is also abrushless drive. An alternator rotative power coupling is used toprovide electrical current to the coil 17. Again, like numbers in thefigures designate similar parts and components.

The embodiment of FIG. 13 is a brushless drive 311 in which the coil 17rotates relative to the armature 19 along with the pole pieces 15. Thedrive 311 operates from a direct current power source and providesdirect current to the coil 17 in order to magnetically couple the polepieces 15 and the armature 19.

The alternator rotative power coupling includes a stationary coil 317,stationary pole pieces 318, a rotating coil 319 and a bridge rectifier329. The alternator rotative power coupling provides current to the coil17 in response to power supplied from the direct current power source.The power source is electrically connected to the stationary coil 317which is located within the stationary pole pieces 318. The rotatingcoil 319 is located to rotate about the stationary pole pieces 318 andthe stationary coil 317. Application of current from the power sourcethrough the stationary coil 317 causes a magnetic field to be generatedabout the stationary pole pieces 318. Rotation of the rotating coil 319through the magnetic field about the stationary pole pieces 318 inducesan alternating current in the rotating coil 319. The rotating coil 319is electrically connected to the bridge rectifier 329 which converts thealternating current to direct current. The direct current from thebridge rectifier is then supplied to the coil 17. The electricallyenergized coil 17 induces magnetic coupling between the rotating polepieces 15 and the armature 19 causing the armature 19 to rotate anddrive a load.

The structure of the alternator rotative power coupling drive 311 asshown in FIG. 13 will now be described. The structure of the loadportion of the drive 311 including the sheaves 21, bearings 45, andarmature 19 is identical to the load portion of the drive 11 which isdescribed above with reference to FIG. 1. The structure of the hub 13,pole pieces 15, and coil 17 of the drive 311 is also identical to thestructure of the hub 13, pole pieces 15 and coil 17 of the drive 11 andis also identical to the hub 13, pole pieces 15 and coil 17 of the drive211, both of which are described above.

The annular rotating coil 319 is coupled to an inner section 325 whichis bolted to the fan 57 and the pole pieces 15 with bolts 321. The innersection 325 has a first portion 325A, a second portion 325B, and a thirdportion 325C. The first portion 325A of the inner section extendsoutwards from the pole pieces 15 and has an inside diameter slightlylarger than the outside diameter of the hub 13. The first portion 325Aforms a hollow robe. The second portion 325B of the inner sectionextends radially outward from the first portion 325A adjacent the polepieces 15 to the fan 57. The third portion 325C extends from the outerradial edge of the second portion 325B in a direction that is parallelto the first portion 325A. Thus, the third portion 325C also forms ahollow tube. The rotating coil 319 is adhesively bonded to the insidediameter of the third portion 325C and extends around the entire insidediameter of the third portion 325C. Bolts 321 extend through a shoulder328 of the inner section 325 to join the inner section 325 to the polepieces 15.

The rotating coil 319 can be a single phase coil or a three phase coil.

The bridge rectifier 329 is adhered to the outer face of the secondportion 325B. Referring to FIG. 23, the bridge rectifier 329 iselectrically connected between the rotating coil 319 and the coil 17.Wires 331 electrically connect the bridge rectifier 329 with therotating coil 319, and wires 333 extend through the fan 57 and the polepieces 15 to electrically connect the bridge rectifier 329 and the coil17. The bridge rectifier 229 (of FIG. 11) and its connections to thecoils is the same as the bridge rectifier 329 shown in FIG. 23.

The stationary pole pieces 318 are mounted to and supported by a coilmount 335 which remains stationary relative to the coil 17, pole pieces15, and the rotating coil 319. The coil mount 335 is supported on thefirst portion 325A by bearings 337 located about the outside diameter ofthe first portion 325A. The bearings 337 are held in place by a shoulder339 of the coil mount 335 and a snap ring 341 on one side, and by ashoulder 343 of the first portion 325A and the stationary pole pieces318 on the other side.

The coil mount 335 extends radially outward from the bearings 337. Atthe outer radial edge of the coil mount 335 is a lip 345. The lip 345extends towards the pole pieces 15 and provides a surface for mounting ajunction box 351. The coil mount 335 and the inner section 325 of thefan 57 form a cavity 349 in which the rotating coil 319, stationary polepieces 318, and the stationary coil 317 are located.

The stationary pole pieces 318 are located in the cavity 349 and aremounted to a shoulder 350 of the coil mount 335. There are twostationary pole pieces 318, an inner piece and an outer piece. Eachstationary pole piece 318 is made up of an annular portion 361 withpoles 363 extending from the outer diameter of the annular portion 361,and a lip 365 extending from the inner diameter of the annular portion361. The poles 363 on an individual stationary pole piece 318 are spacedapart by gaps. When the stationary pole pieces 318 are assembled asshown, the poles 363 of the inner and outer stationary pole pieces 318are interdigitated so as to form alternating magnetic polarities aroundthe circumference of the assembly of the stationary pole pieces 318.

The assembled stationary pole pieces 318 encircle the stationary annularcoil 317. The stationary coil 317 is located between and is encircled bythe annular portions 361, the poles 363, and the lips 365 of thestationary pole pieces 318. The inner and outer stationary pole pieces318 are bolted together about the stationary coil 317 with bolts 367.The assembled stationary pole pieces 318 encompassing the stationarycoil 317 are mounted to the shoulder 350 of the coil mount 335 withbolts 369. The mounted stationary pole pieces 318 and stationary coil317 extend around the circumference of the first portion 325A and areseparated therefrom by a gap 371. The inner stationary pole pieces 318are separated from the bridge rectifier 329 by gap 375. These gaps 371,375 are provided so that the pole pieces 318 remain stationary withoutinterfering with the rotating first portion 325A and bridge rectifier329.

The poles 363 of the stationary pole pieces 318 are separated from therotating coil 319 by a gap 373.

Current is supplied to the stationary coil 317 from an electrical powersource through wires 353. The wires 353 extend from the stationary coil317 through the stationary pole pieces 318 and the coil mount 335 to ajunction box 351. A conduit is used to couple the junction box 351 andthe coil mount 335 to a fixed or stationary platform, such as the motor.Thus, the pole pieces 318 and coil 317 are stationary, while the coil319, the pole pieces 15 and the coil 17 are rotating at motor speed. Thejunction box 351 is anchored to the coil mount 335 with screws (notshown).

A bracket 355 is coupled to the conduit 351. The bracket 355 is orientedto extend over the armature 19. The speed sensor 103 is mounted to anextension portion 101 of the bracket 355 to detect movement of thearmature 19.

In operation, dc current is provided to the stationary coil 317 in orderto energize the coil 17. As dc current is provided to the stationarycoil 317, a magnetic field is created between the poles 363. Thismagnetic field extends across the gap 373 to the rotating coil 319,wherein alternating current is induced into the rotating coil. Theinduced current is converted to dc by the bridge rectifier 329, which dccurrent is then used to energize the coil 17.

To vary the amount of current supplied to the coil 17 and thus thecoupling of the armature 19 to the pole pieces 15, the voltage and/orcurrent provided to the stationary coil 317 is varied. When little or nocurrent is supplied to the stationary coil 317, the coil 17 is notsufficiently energized and little or no coupling occurs between thearmature 19 and the pole pieces 15. Thus, the armature 19 does notrotate. As more current is applied to the stationary coil 317, morecurrent is induced into the rotating coil 319 and more current isprovided to the coil 17 in order to rotate the armature.

The alternator rotative coupling drive 311 of FIG. 13 is brushless andtherefore requires less maintenance than drives that use brushes. Thedrive 311 also is more efficient than drives requiring a gap between thecoil and the pole pieces since no gap is required between the coil andpole pieces of drive 311.

In FIG. 14 there is shown a drive 411 of the present invention, inaccordance with a still further embodiment. The drive 411 utilizes aliquid conductor rotative coupler 417 to supply current to the coil 17.Again, like numbers in the figures designate similar parts andcomponents. The embodiment of FIG. 14 is a brushless drive in which thecoil 17 rotates relative to the armature 19 along with the pole pieces415. The drive 411 operates from a direct current power source andprovides direct current to the coil 17. The coil 17 is encompassed bythe pole pieces 415 so that no gap separates the coil 17 and pole pieces415 thereby providing efficient magnetic coupling between the coil 17and the pole pieces 415 when the coil 17 is electrically charged.

A mercury coupler 417 electrically connects the coil 17 and the powersource so that current may be supplied to the coil 17 from the powersource through the mercury coupler 417. The mercury coupler 417 has aninner housing 419 and an outer housing 421. The inner and outer housings419 and 421 are rotatable with respect to each other. Electricalcontacts couple the inner and outer housing 419 and 421 so thatelectrical power may be transmitted between the inner and outer housings419 and 421. The electrical power source is electrically connected tothe inner housing 419 and the coil 17 is electrically connected to theouter housing 421. The inner housing 419 remains stationary relative tothe coil 17 while the outer housing 421 rotates with the coil 17.Current is transmitted from the power source through the inner housing419 to the outer housing 421 and from the outer housing 421 to the coil17. The current in the coil 17 causes the pole pieces 15 to magneticallycouple the armature 19, rotating the armature 19 and driving a load.

The structure of the mercury rotative electrical connector drive 411 asshown in FIG. 14 will now be described. The structure of the loadportion of the drive 411 including the sheaves 21, bearings 45, andarmature 19 is identical to the load portion of the drive 11 which isdescribed above with reference to FIG. 1. The structure of the hub 13,pole pieces 15, and coil 17 of the drive 411 is identical to thestructure of the hub 13, pole pieces 15 and coil 17 of the drive 11 ofFIG. 1 and is also identical to the hub 13, pole pieces 15 and coil 17of the drive 211 of FIG. 11, both of which are described above. The fan57 is coupled to the outer pole piece 15 with bolts 423 and rotates withthe pole pieces 15 and the coil 17.

The mercury coupler 417 is coupled to the outer end of the hub 13. Theouter housing 421 of the mercury coupler 417 is located in thecylindrical cavity 29 of the hub 13 opposite the shaft 31 of the motor33. The outer housing 421 is secured to the hub 13 with a suitableadhesive. The outer housing 421 is rotated by the hub 13 along with thecoil 17 and the pole pieces 15 when the hub 13 is rotated by the motorshaft 31. The inner housing 419 of the mercury coupler 417 extends outof the outer housing 421 away from the hub 13. The mercury coupler isthus located so that its axis of rotation is coaxial with the axis ofrotation of the drive 411.

Contacts 425 extend from the outer housing 421 of the mercury coupler417 so that the coil 17 may be electrically connected to the outerhousing 421. Wires 427 couple to the contacts 425 and extend through thehub 13, fan 57 and pole pieces 15 to the coil 17. Contacts 429 extendfrom the inner housing 419 so that the inner housing 419 may beelectrically connected to a power source.

Referring now to FIG. 15, the mercury coupler 417 will be described infurther detail. The mercury coupler 417 is conventional and commerciallyavailable. The outer housing 421 is rotatively located about the innerhousing 419 on sealed bearings 431. The bearings 431 are pressed fitbetween the inner and outer housings 419 and 421. A snap ring 435 is onthe outer end of the bearing 431. A gap 436 extends between the innerand outer housings 419 and 421 at the inner end of the inner housing419E so that the housings 419 and 421 may move relative to each other.

The inner and outer housings 419 and 421 are electrically connected bymercury 437 or some other liquid conductor located in channels 439 and441 which conductively couples inner contact rings 443 and 445 of theinner housing 419 and outer contact rings 447 and 449 of the outerhousing 421. The respective contacts 429 are electrically connected tothe respective inner contact rings 443 and 445 with wires 451 whichextend through the inner housing 419. The inner contact rings 443 and445 are secured to the inner housing 419 and extend from the innerhousing 419 into the channels 439 and 441, respectively, a sufficientdistance to contact the mercury 437 in the channels 439 and 441. Theouter ring contacts 447 and 449 are located in the outer housing 421adjacent the channels 439 and 441, respectively, so that the outerringcontacts 447 and 449 contact the mercury 437 in the channels 439 and441. Respective contacts 425 are electrically connected to therespective outer ring contacts 447 and 449 with wires 453 which extendthrough the outer housing 421. The contacts 425 and 429, wires 451 and453, inner contact rings 443 and 445, mercury 437, and outer contactrings 447 and 449 are arranged so that two continuous conductive pathsmay be formed through the coupler 417.

The mercury 437 is retained within the respective channels 439 and 441by seals 455, 457 and 459, The channel 439 is formed between the sealedbearings 431, the outer housing 421, the inner housing 419, and ashoulder 461 of the inner housing 419. The seal 455 extends between theinner and outer housings 419 and 421 along the bearings 431 to preventmercury 437 from seeping through the bearings 431. The seal 457 extendsbetween the shoulder 461 and the outer housing 421 to prevent mercury437 from moving between channel 439 and channel 441. The channel 441 isformed between the outer housing 421, the inner housing 419, theshoulder 461, and another shoulder 463 of the inner housing 419. Theseal 459 extends between the shoulder 463 and the outer housing 421 toprevent mercury from escaping from channel 441 into the gap 436.

Referring back to FIG. 14, a bracket 465 is mounted to extend over thearmature 19. The bracket 465 is mounted on bearings 467 so that thebracket 465 is held stationary relative to the coil 17, pole pieces 15,and the fan 57. The bearings 467 are mounted to the outer housing 421 ofthe mercury coupler 417. The inner face of the bearings 467 is held inplace on the mercury coupler 417 by snap rings 469 and 471. The outerface of the bearings 467 is held in place by snap ring 473 and ashoulder 475 of the bracket 465. The bracket 465 extends radiallyoutward from the bearings 467. At the outermost radial position of thebracket 465 an extension portion 101 of the bracket 465 extends backover the armature 19. A speed sensor 103 is mounted to the extensionportion 101 to detect rotation of the armature 19.

In operation, the inner housing 419 is secured to a fixed platform, suchas the motor 33, by way of a conduit, such as is shown in FIG. 1.Electrical current is supplied to the coil 17 by way of the coupling417.

Although the coupling 417 has been described as having its outer housing421 coupled to a rotating part of the drive, the outer housing could becoupled to a stationary platform and the inner housing 419 is thencoupled to a rotating part (such as the hub) of the drive.

The power coupler devices of FIGS. 11, 13 and 14 could be used on adrive where the armature is coupled to the motor shaft (for example, byway of a hub) and the coil 17 and pole pieces are coupled to the load.

All of the drives 11, 111, 211, 311, 411 discussed above may beconfigured with various input and output structures. FIGS. 16-19illustrate the various input and output configurations of the exemplarydrive 211. However, the illustrated input/output configurations of drive211 may also be utilized in the drives 11, 111 and 311.

Referring now to FIG. 16, a through shaft version of the drive 211 isshown. The hub 13 extends completely through the drive. The motor 33 canbe located at either end of the hub 13. The hub 13 accepts the motorshaft 31 at either end of the hub 13. The hub 13 has shoulders 261 and263 at each end of the hub which are formed by sections of the hubhaving a narrower diameter than the body of the hub. The clamping device265 may be clamped about either shoulder 261 or 263 to clamp the motor33 to the hub 13. The through shaft configuration of the drive providesflexibility in the orientation of the drive with respect to the motor 33and the load (which is coupled to the sheaves 21 ). The motor may belocated at the same end of the drive as the sheaves 21 which drive theload, or the motor may be located at the opposite end of the drive fromthe sheaves 21.

Referring now to FIG. 17, an inverted sheave version of the drive 211 isshown. The hub 13 extends completely through the drive. The motor (notshown) is located at the opposite end of the drive from the sheaves 21which drive the load. The hub 13 accepts the motor shaft (not shown)opposite the load end 13L of the hub. The hub 13 has a shoulder 271 atthe end of the hub 13 which accepts the motor shaft. The clamping device265 may be clamped about the shoulder 271 to clamp the motor to the hub13. The inverted sheave drive is useful when the load is located in aconfirmed area. The motor may be located away from the confined area andthe sheaves 21 may be coupled to the load.

Referring now to FIG. 18, a shaft in-shaft out version of the drive 211is shown. The motor shaft (not shown) provides the input to the driveand an output shaft 275 provides output from the drive. The output shaft275 is used to drive the load. The output shaft 275 has a shaft portion277 and a flange 279. The shaft portion 277 is aligned in line with thecylindrical cavity 29 of the hub 13 adjacent the end of the hub 13Eseparated from the hub by a gap 281 so that rotation of the hub 13 doesnot influence the shaft portion 275. The flange 279 integrally couplesand extends radially from the shaft portion 277 adjacent the gap 281.The flange 279 is secured to a shaft mount 283 with bolts 285. The shaftmount 283 rides on bearings 45 and is coupled to the armature 19 by theradial wall 53. The shaft 275, therefore, is rotated by the armature 19when the armature 19 is rotated due to magnetic coupling between thearmature 19 and the pole pieces 15.

The motor (not shown) is coupled to the drive opposite the output shaft275. The hub 13 receives the motor shaft in the cylindrical cavity 29opposite the end of the hub 13E adjacent the shaft 275. The hub 13 has ashoulder 287 about which a clamping device 265 may be located forclamping the hub 13 to the motor. The motor and the output shaft 275 arelocated relative to one another so that the shaft in-shaft out drive maybe coupled in line between the motor and the load. The shaft in-shaftout drive is useful for driving loads such as a pump or a gear box.

Referring now to FIG. 19, a shaft in-flexible coupling out version ofthe drive 211 is shown. The motor shaft (not shown) provides the inputto the drive and the flexible coupling 291 provides output from thedrive. The flexible coupling 291 is used to drive the load. Conventionalcommercially available flexible couplings such as that described in U.S.Pat. No. 3,283,535 may be used as the flexible coupling 291.

The flexible coupling 291 is located in line with the axis of the hub13. The flexible coupling 291 has a rigid inner ranged portion 292, aflexible center portion 293, and a rigid load coupling portion 294. Theinner ranged portion 292 is located adjacent an end of the hub 13E andbearings 45, separated from the hub and bearings 45 by a gap 295. Theinner ranged portion 292 is coupled to a coupling mount 296 with bolts297. The coupling mount 296 is located on the bearings 45 and is coupledto the armature 19 by the radial wall 53. The inner ranged portion 292,flexible center portion 293, and load coupling portion 294 are coupledtogether so that a load coupled to the load coupling portion 294 isjoined to the armature through the flexible center portion 293 and theinner ranged portion 292. Therefore, the flexible coupling 291 isrotated by the armature 19 when the armature 19 is rotated due tomagnetic coupling between the armature 19 and the pole pieces 15.

The motor (not shown) is coupled to the drive end that is opposite theflexible coupling 291. The hub 13 receives the motor shaft in thecylindrical cavity 29 opposite the end of the hub 13E adjacent theflexible coupling 291. The hub has a shoulder 298 about which a clampingdevice 265 may be located for clamping the hub to the motor. The motorand the flexible coupling 291 are located relative to one another sothat the drive may be coupled generally in line between the motor andthe load. The flexible center portion 293 of the flexible coupling 291allows the load to be misaligned from an in-line position with respectto the motor. The shaft in-flexible coupling out drive is useful fordriving loads such as pumps or gear boxes.

Although the present invention has been described as using Lundberg typeof pole pieces, other types of magnetic poles could be used. Forexample, salient type poles could be used without departing from thespirit and scope of the present invention.

In FIG. 20, there is shown a drive 511 with a speed sensor 103 mountedto a rotating part. The speed sensor 103 is used to monitor the speed ofthe output member (such as the armature 19 and sheave assembly shown inFIG. 20). Traditionally, a speed sensor 103 has been mounted to astationary or non-rotating pan, such as is shown in FIG. 1. In such anarrangement, the speed sensor is stationary. Electrical wires directlyconnect the speed sensor to a control circuit 514 or to a monitoringcircuit. The control circuit is typically mounted off of the drive andon a stationary platform.

However, in the drive 511 shown in FIG. 20, the speed sensor 103 ismounted to a rotating part. Thus, the speed sensor 103 can be mounted toeither the armature 19 or to the pole pieces 15. When the speed sensoris mounted to one of the rotating members, notches are formed in theother rotating member. Thus, the differential speed between the tworotating portions (the armature and the pole pieces) of the drive issensed.

For example, as shown in FIG. 20, the speed sensor 103 can be mounted ina cavity 515 in one of the pole pieces 15. Notches 517 are machined intothe inside surface 519 of the armature 19 so as to form peaks andgrooves as described above with reference to FIG. 2. The notches extendfor a short distance from the end 521 of the armature. Alternatively,the speed sensor 103A can be mounted onto the fan 57, as shown by dashedlines in FIG. 20. Notches 525 are machined into the end 521 of thearmature so as to form peaks and grooves as described with reference toFIG. 2. Wherever the speed sensor is located, the sensor head 523 of thespeed sensor is located adjacent to the notches. A gap separates thesensor head from the notches so as to avoid direct contact.

In the preferred embodiment, the speed sensor 103 is a magnetic variablereluctance sensor, which is conventional and commercially available.Referring to FIG. 21, the electrical connections of the speed sensorwill be described. The speed sensor 103 is a three wire device, havingthe following wires: power 531, ground 533 and signal 535. The power andground wires 531, 533 are connected to a power supply 537, in parallelwith the eddy current coil 17. A dropping resistor R is placed in serieswith the power wire 531 and a zenor diode D is connected across thepower and ground wires 531, 533. A voltage regulator could be used inplace of the resistor and diode. The signal wire 535 is connected to alight source 539, such as a lift emitting diode (LED). The LED isconnected between the signal wire 535 and the ground wire 533.

Referring back to FIG. 20, the LED is located on a hollow end shaft 541.The rotatable end shaft 541 has a flange 542 which is coupled to the fan57, the pole pieces 15 and the hub 13. Thus, the LED 539 rotates inunison with the speed sensor 103 and its power supply. As shown in FIG.20, the power supply is a rotating coil 219 of a rotary transformer,which has been previously discussed with reference to FIG. 11. Thecross-sectional shape of magnetically susceptible elements of FIG. 20are different. The stationary member 535 is shaped like an inverted "U",creating air gaps 540, 547 between the stationary member and the endshaft 541.

The LED 539 is preferably located along the rotative axis of the drive.A light sensor 543 is located on a stationary housing 536, preferablyalong the same axis of rotation as the light source. In the preferredembodiment, the light sensor 543 is a photo transistor. Wires extendfrom the light sensor 543 to a junction box 251, where connections aremade to the appropriate circuit. An air gap separates the LED 539 fromthe light sensor 543. The stationary housing 536 is anchored to a fixedplatform in the mariner previously discussed with reference to the otherembodiments. Thus, the stationary housing 536 does not rotate.

In operation, the speed sensor 103 generates electrical pulses based onthe differential speed between the armature and the pole pieces.Referring to FIG. 21, a pulse is generated whenever the sensor head 523passes adjacent to a peak 107, followed by a notch 105 in the armature19. The pulses generated by the speed sensor 103 are used to directlydrive the LED 539. The LED 539 thus produces pulses of light in directproportion to the electrical pulses produced by the speed sensor.Alternatively, the light source can produce a greater number or fewernumber of pulses in proportion to each speed sensor pulse.

The light pulses are received by the photo transistor 543. The phototransistor converts the light pulses to electrical pulses, which arethen transmitted to the control circuit 514 by wires 545.

The frequency of the pulses produced by the speed sensor 103 isproportional to the differential speed between the pole pieces 15 andthe armature 19. If the armature 19 is not rotating at all, then thedifferential speed will be at a maximum speed (because the pole piecesare rotating at the same speed as the motor shaft) and the pulsefrequency will be at a maximum frequency. If the armature is rotating atthe same speed as the pole pieces, then the differential speed is 0 andthe pulse frequency is 0. Intermediate armature speeds will produceintermediate pulse frequencies.

The speed sensor arrangement shown in FIG. 20 can be used with any powersupply. For example, the rotary transformer shown in FIG. 11 can be usedas the power supply. Specifically, the power supply includes therotating coil 219 and bridge rectifier 229. The speed sensor 103 isconnected to the output of the bridge rectifier 229. Alternatively, thepower supply can include the coil 319 and bridge rectifier 329 of FIG.13. Still another way to power the speed sensor is to connect the speedsensor to the coupling 417 of FIG. 14.

The speed sensor 103 shown in FIG. 21 is a three wire speed sensor. Sucha speed sensor produces digital pulses. Other types of speed sensors canbe used. For example, a two wire, self powered, speed sensor 103B can beused, as shown in FIG. 22. The speed sensor is not connected to thepower supply. The speed sensor produces sine wave pulses which pulsesdrive the LED 539.

In FIGS. 24-26 a drive 611 in accordance with another embodiment isshown. This embodiment uses a bearing power coupling for providingcurrent to the rotating coil 17. Electrical current is provided from astationary power supply to the rotating coil directly through one ormore bearings 613, 615. Thus, the drive is brushless. Because there areno brushes, routine maintenance on the drives (which is usually forreplacing brushes) is reduced.

Furthermore, the use of a stub shaft 630 at one end of the drive (whichis opposite the motor shaft 31 in FIG. 24) allows sizing of the powercoupling member independently of the hub. One size (or horsepower) drivewill require a hub 13 of a first diameter, while a larger horsepowerdrive will typically require a larger diameter hub. But, the stub shaft630 need not change size; the same size stub shaft can be used on boththe small and larger drives. This allows the same bearing to be used. Inaddition, a relatively small sized bearing can be used because thebearings 613, 615 need not encircle the hub 13. These factors make thedrive 611 more economical to manufacture.

The bearing power coupling will be now described more specifically.Referring to FIG. 24, the stub shaft 630 is coupled to the fan 57 inmanner that is similar to the slip ring shaft 63 of FIG. 1 being coupledto the fan. Referring to FIG. 25, the stub shaft 630 has first andsecond outer cylindrical surfaces 670, 690. The first outer surface 670is located at the outer end of the shaft 630. A non-conductive ring 619is located on the first outer surface 670. A key 621 extends between thenon-conductive ring 619 and the shaft 630, in order to rotate thering619 in unison with the shaft. The ring is positioned on the shaftfirst outer surface 670 by a spacer 623 that abuts a shoulder 625. Thespacer 623 contacts one end of the ring 619, while an end plate626.contacts the other end of the ring. The plate 626 is secured to theouter end of the shaft by a threaded fastener 627. Thus, the ring 619 iscoupled to the shaft 630 by the key 621, the spacer 623, the shoulder625, and the plate 626.

A pair of conductors 629 are located on the outer surface of the ring619. The conductors 629 are bonded to the ring 619 so as to rotate inunison therewith. The conductors 629 can be rings that extend around thenon-conductive ring619. Alternatively, the conductors 629 can be shortstrips that do not fully extend around the circumference of thenon-conductive ring 619. The conductors 629 are spaced apart from eachother so as to avoid contact with each other. The conductors 629 can bebonded to or press fit on the ring619. Each conductor has a contact 631that emerges from the outer end of the ring 619 and the plate 626. Wires633 are connected to the contacts 631, which wires are connected to thedrive coil 17 so as to provide a drive coil circuit. The wires 633extend through channels 635 (see FIG. 26) in the shaft 630 oralternatively in the ring 619.

Mounted on each conductor 629 is a bearing 613 or 615. Each bearing hasan inner raceway 637, an outer raceway 639, and plural rollers 641 (forexample, balls, rollers or needles). The inner raceway 637 is press fitonto the respective conductor 629. A non-conductive spacer 643 (forexample, an annular printed circuit board) is located between both outerraceways 639. In addition, if the housing 645 is conductive, then anon-conductive spacer 643 is provided between an outer raceway and thehousing 645. A stationary wire 647 is electrically connected to eachouter raceway. In the preferred embodiment, a band 649 is clamped orpressed fit to the outside diameter of each outer raceway and end ofeach wire is interposed between the respective band 649 and therespective outer raceway 639. Alternatively, the wires 647 can be bondedto the outer raceways 639 or to the bands 649. The wires 647 extend to aconduit 93 (see FIG. 26), which is anchored to a stationary platform.

The wires 647 are connected to a voltage source, which preferablyprovides a variable voltage.

The housing 645 is located around the bearings 613, 615. A pottingcompound 651 is located in the cavity between the housing 645 and theouter raceways 639. The potting compound 651 both seals the electricalconnection of the wires 647 to the bearings and provides structuralsupport for the housing on the bearings. Use of the potting compoundmakes assembly of the housing onto the bearings simpler because themanufacturing tolerances can be wide. The housing has openings 653 forreceiving the shaft 630.

Referring to FIG. 24, another bearing 655 is located on the second outersurface 690 of the shaft 630. An extension member 25 is coupled to theouter raceway of the bearing 655 and extends from the bearing to aradial distance beyond the armature. A speed sensor 103 is positionedadjacent to the armature 19 by the extension member 25.

The housing 645 and the outer raceways 639 are prevented from rotatingwith the shaft 630 by the extension member 25. The extension memberitself is prevented from rotating by the conduit 93 (see FIG. 26). Asshown in FIG. 26, the extension member has two posts 657 that extendaxially. The posts form a notch 659, which receives a portion of thehousing 645. Thus, the housing is prevented from rotating by the twoposts.

In operation, the motor shaft 31 rotates the hub 13, the coil 17, thefan 57, the shaft 630 and the inner raceways 637 of the bearings 613,615. To rotate the armature 19 and the sheaves 21, the coil isenergized. Electrical current is applied to the drive coil 17 from thestationary wires 647, to the outer raceways 639 of the bearings, to theballs 641 which are in electrical contact with the outer raceways, tothe inner raceways 637 which are in electrical contact with the balls,to the wires 633 and to the drive coil 17. Of course, a complete circuitis made, so that current enters the drive coil through one bearing andexits through the other bearing (for dc). Alternating current (ac) couldalso be used. However, a rectifier is connected between the bearings613, 615 and the drive coil in order to rectify the ac current. To varythe speed of the sheaves, the current through the bearings 613, 615 isvaried. The variation in current is done by a controller located off ofthe drive.

The bearings conduct current, even if they contain a lubricant such asgrease.

In FIG. 27, there is shown another embodiment of the bearing powercoupling. In this embodiment, the extension member 661 for the speedsensor 103 is mounted to the shaft 630 by way of the bearings 613, 615.The extension member 661 is a conduit having one end coupled to thehousing 645. The stationary wires 647 traverse through the conduit 641.The other end of the conduit 661 (which may have one or more bendstherein) is coupled to a stationary object. The speed sensor 103 iscoupled to the conduit by an arm 663. The arm 663 is clamped to theconduit 661 by a screw 665. The screw 665 can be loosened to allow thearm to be moved along the conduit. This permits radial adjustment of thespeed sensor 103 relative to the shaft 630.

In FIG. 28, there is shown still another embodiment of the bearing powercoupling. In this embodiment, an output shaft 671 is provided in lieu ofsheaves. The drive 611A of FIG. 28 is a shaft-in shaft-out drive.

The output shaft 671, which rotates in unison with tile drive coil 17,supports the two bearings 613, 615 that provide electrical current tothe drive coil. The wires 633 that are connected to the inner racewaysof the bearings need not go through the shaft 671 or ring619. The wires633 traverse a channel in a radial flange 675 that is integral to theshaft.

The armature 19 is bolted to the hub 13, while tile fan 57 is bolted tothe armature. The pole pieces 15 are mounted to the hub 13 by bearings677. The output shaft 671 is bolted to the pole pieces 15 by way of theflange 675. The flange 675 has holes 679 that are spaced apart andarranged in a circular pattern of constant radius from the axis ofrotation of the shafts. The holes 679 form teeth that are similar to theteeth 105 of FIG. 1, so as to form a digital pattern for speed sensingpurposes. The teeth are thus on an end of the drive instead of beingaround an outside diameter of the drive. The speed sensor 103 is coupledto the housing so as to be adjacent to the teeth.

Although the invention has been described with a rigid conduit 93 forpreventing rotation of the stationary wires, the wires themselves canperform this function if they are sufficiently stiff. Alternatively, aflexible cable or conduit can be used.

The foregoing disclosure and the showings made in the drawings aremerely illustrative of the principles of this invention and are not tobe interpreted in a limiting sense.

We claim:
 1. A variable speed shaft mounted eddy current drive,comprising:a first rotatable member that comprises pole pieces and adrive coil; a second rotatable member that comprises an armature; one ofsaid first rotatable member or said second rotatable member comprising ahub that is structured and arranged to be rotated by a motor, the otherof said first rotatable member or said second rotatable member beingstructured and arranged to be coupled to a load; said hub has first andsecond ends, said hub first end being structured and arranged to bemounted to said motor; a shaft coupled to said first rotatable member,said shaft being located adjacent to said hub second end; said polepieces having plural interdigitated poles, said poles being separatedfrom said armature by a gap; said drive coil located adjacent to saidpole pieces, said pole pieces providing a path for a magnetic fieldproduced by said drive coil, wherein when electrical current is providedto said drive coil the other of said first rotatable member or saidsecond rotatable member rotates due to coupling between said pole piecesand said armature; a stationary electrical conductor; a bearing havingfirst and second raceways and rollers in contact with said first andsecond raceways, said first raceway being coupled with said drive coilso as to rotate in unison with said drive coil, said first raceway beingelectrically connected to said drive coil, said second raceway beingcoupled to said stationary conductor and being electrically connected tosaid stationary conductor, said first raceway rotating with respect tosaid second raceway, said first and second raceways being electricallycoupled together by way of said rollers, said bearing first racewaybeing mounted to said shaft so as to rotate in unison therewith.
 2. Thevariable speed drive of claim 1, wherein said first rotatable membercomprises said hub, said pole pieces being coupled to said hub, saidfirst rotatable member also comprising a fan that is coupled to at leastone of said pole pieces, said shaft being coupled to said fan.
 3. Thevariable speed drive of claim 1, wherein said other of said firstrotatable member or said second rotatable member that is structured andarranged to be coupled to said load comprises said first rotatablemember and said shaft is an output shaft that is structured and arrangedto receive a load.
 4. The variable speed drive of claim 3, furthercomprising:a speed sensor coupled to said bearing second raceway; adigital pattern on said first rotatable member, said digital patternlocated adjacent to said speed sensor.
 5. The variable speed drive ofclaim 1, wherein said other of said first rotatable member or saidsecond rotatable member that is structured and arranged to be coupled tosaid load comprises said second rotatable member and said secondrotatable member comprises a sheave that is located adjacent to said hubfirst end.
 6. The variable speed drive of claim 1, wherein said bearingis an electrical power coupling bearing, further comprising:a secondbearing located on said shaft; an extension coupled to said secondbearing, said extension extending radially from said shaft; a speedsensor coupled to said extension and located adjacent to said other ofsaid first rotatable member or said second rotatable member that isstructured and arranged to be coupled to said load.
 7. The variablespeed drive of claim 1, further comprising:a housing located around saidbearing; said housing being coupled to said bearing second raceway bypotting compound.
 8. The drive of claim 1 wherein said hub has anoutside diameter, said shaft being sized independently of said huboutside diameter.
 9. A variable speed shaft mounted eddy current drive,comprising:a first rotatable member that comprises pole pieces and adrive coil; a second rotatable member that comprises an armature; one ofsaid first rotatable member or said second rotatable member comprising ahub that is structured and arranged to be rotated by a motor, the otherof said first rotatable member or said second rotatable member beingstructured and arranged to be coupled to a load; said pole pieces havingplural interdigitated poles, said poles being separated from saidarmature by a gap; said drive coil located adjacent to said pole pieces,said pole pieces providing a path for a magnetic field produced by saiddrive coil, wherein when electrical current is provided to said drivecoil the other of said first rotatable member or said second rotatablemember rotates due to coupling between said pole pieces and saidarmature; a first stationary electrical conductor; a first bearinghaving first and second raceways and rollers in contact with said firstand second raceways, said first bearing first raceway being coupled withsaid drive coil so as to rotate in unison with said drive coil, saidfirst bearing first raceway being electrically connected to said drivecoil, said first bearing second raceways being coupled to saidstationary conductor and being electrically connected to said stationaryconductor, said first bearing first raceway rotating with respect tosaid first bearing second raceway, said first bearing first and secondraceways being electrically coupled together by way of said rollers; asecond bearing having first and second raceways and rollers in contactwith said first and second raceways, said second bearing first racewaybeing electrically connected to said drive coil so as to form a circuitthrough said drive coil with said first bearing first raceway, saidsecond bearing second raceway being electrically coupled to a secondstationary conductor, said second bearing first and second racewaysbeing electrically coupled together by way of said second bearingrollers.
 10. The variable speed drive of claim 9, wherein said hub hasfirst and second ends, said hub first end being structured and arrangedto be mounted to said motor, further comprising:a shaft coupled to saidfirst rotatable member, said shaft being located adjacent to said hubsecond end; said first bearing first raceway and said second bearingfirst raceway being mounted to said shaft so as to rotate in unisontherewith.
 11. A variable speed drive, comprising:a first rotatablemember that comprises pole pieces and a drive coil; a second rotatablemember that comprises an armature; one of said first rotatable member orsaid second rotatable member comprising a hub, the other of said firstrotatable member or said second rotatable member being structured andarranged to be coupled to a load; said pole pieces having pluralinterdigitated poles, said poles being separated from said armature by agap; said drive coil located adjacent to said pole pieces, said polepieces providing a path for a magnetic field produced by said drivecoil; said hub having first and second ends, said hub first end havingan opening for receiving a motor shaft said hub being structured torotate about an axis of rotation; an electrical stationary conductor; afirst conductor that is coupled to said first rotatable member so as torotate in unison with said drive coil, said first conductor beingannular and being electrically connected to said drive coil; a secondconductor that is coupled to said stationary conductor so as to bestationary, said second conductor being electrically connected to saidstationary conductor; a liquid conductor located between said firstconductor and said second conductor so as to be in electrical contactwith said first and second conductors; said first conductor, said secondconductor and said liquid conductor being located adjacent to said hubsecond end.
 12. The variable speed drive of claim 11 wherein said firstand second conductors each have an outside diameter and said hub has anoutside diameter, said outside diameters of said first and secondconductors being less than said outside diameter of said hub.
 13. Thevariable speed drive of claim 11 wherein said first and secondconductors and said liquid conductor are contained in a housing, saidhousing being received by a bore that is adjacent to said hub secondend.
 14. The variable speed drive of claim 11 wherein said firstconductor is coupled to a rotor, said second conductor is coupled to astator, said stator being located inside of said rotor, said rotorforming a housing around said liquid conductor and being coupled withsaid drive coil, said rotor and said stator being rotatably coupledtogether by a bearing.
 15. The variable speed drive of claim 14 whereinsaid rotor has an end and said stator has an end, said first conductorexiting said rotor from said rotor end, said second conductor exitingsaid stator from said stator end.
 16. The variable speed drive of claim14, further comprising:a second bearing coupled with said rotor; a speedsensor coupled with said second bearing and located adjacent to theother of said first rotatable member or said second rotatable memberthat is structured and arranged to be coupled to a load.
 17. Thevariable speed drive of claim 14 further comprising a fan coupled withsaid pole pieces so as to be adjacent to said hub second end.
 18. Thevariable speed drive of claim 14 wherein the other of said firstrotatable member or said second rotatable member that is structured andarranged to be coupled to a load further comprises a sheave, said sheavebeing located adjacent to said hub first end.
 19. A variable speeddrive, comprising:a rotatable member comprising a hub having first andsecond ends, said hub first end having an opening for receiving a motorshaft, said hub having a size that is large enough for said hub firstend to receive said motor shaft; an output member that is rotatablymounted to said rotatable member, said output member being structuredand arranged to be coupled to a load; an electromagnet located adjacentto an armature, said electromagnet being coupled to a one of saidrotatable member or said output member, said armature being coupled toan other of said rotatable member or said output member; an electricalcoupling comprising a first stationary conductor, a first rotatableconductor, a second stationary conductor, and a second rotatableconductor, said first stationary conductor comprising a ring, said firstrotatable conductor comprising a ring, said first stationary conductorand said first rotatable conductor being electrically coupled togetherby a first liquid conductor, said second stationary conductor beingelectrically coupled to said second rotatable conductor by a secondliquid conductor, one of said second stationary conductor or said secondrotatable conductor extending through at least one of said rings; saidelectrical coupling being sized independently of said hub size; saidelectrical coupling being contained within a housing, said housing beingreceived by a bore in said one of said rotatable member or said outputmember, said electrical coupling being located adjacent to said hubsecond end.
 20. A variable speed drive, comprising:a rotatable memberthat is structured and arranged to be rotated by a motor; an outputmember that is rotatably mounted to said rotatable member, said outputmember being structured and arranged to be coupled to a load; anelectromagnet located adjacent to an armature, said electromagnet beingcoupled to a one of said rotatable member or said output member, saidarmature being coupled to an other of said rotatable member or saidoutput member; a speed sensor directly coupled to one of saidelectromagnet or said armature so as to rotate with said one of saidelectromagnet or said armature; a periodically changing pattern locatedon an other of said electromagnet or said armature, said pattern beingsensible by said speed sensor; a signal transmitter coupled to saidspeed sensor so as to rotate with said speed sensor, said signaltransmitter being connected to said speed sensor; a signal receiverlocated on a third member so as to receive a signal produced by saidsignal transmitter, said third member being stationary relative torotation of said electromagnet and said armature.
 21. A variable speeddrive, comprising:a first rotatable member that comprises pole piecesand a drive coil; a second rotatable member that comprises an armature;one of said first rotatable member or said second rotatable membercomprising a hub, the other of said first rotatable member or saidsecond rotatable member being structured and arranged to be coupled to aload; said pole pieces having plural interdigitated poles, said polesbeing separated from said armature by a gap; said drive coil locatedadjacent to said pole pieces, said pole pieces providing a path for amagnetic field produced by said drive coil; said hub having first andsecond ends, said hub first end having an opening for receiving a motorshaft, said hub being structured to rotate about an axis of rotation; asolid shaft that is coupled to said first rotatable member, said shaftlocated adjacent to said hub second end, said shaft being structured andarranged to rotate about said axis of rotation; a rotating conductorcoupled to said shaft, said rotating conductor being electricallycoupled to said drive coil; a stationary conductor rotatably coupled tosaid shaft, said stationary conductor being electrically coupled to saidrotating conductor and being stationary relative to said rotatingconductor.
 22. A variable speed drive, comprising:a first rotatablemember that comprises alternating north and south poles and a drivecoil; a second rotatable member that comprises an armature; one of saidfirst rotatable member or said second rotatable member comprising a hub,the other of said first rotatable member or said second rotatable membercomprising a sheave for coupling to a load; said poles being separatedfrom said armature by a gap; said drive coil located adjacent to saidpoles, said poles providing a path for a magnetic field produced by saiddrive coil; said hub having first and second ends, said hub first endhaving an opening for receiving a motor shaft, said hub being structuredto rotate about an axis of rotation; a rotating support coupled to saidfirst rotatable member and located adjacent said hub second end, saidrotating support being structured and arranged to rotate about said axisof rotation; plural rotating conductors coupled to said rotating supportso as to rotate therewith, said rotating conductors being electricallycoupled to said drive coil; said hub has an outside diameter and saidrotating conductors each have an outside diameter, with said hub outsidediameter being greater than each of the outside diameters said rotatingconductors; plural stationary conductors, each of which is electricallycoupled to a respective one of said rotating conductors; a stationarysupport coupled to said plural stationary conductors, said stationarysupport being coupled to said rotating support by way of a bearing, saidbearing being electrically isolated from said rotating conductors andsaid stationary conductors.
 23. The variable speed drive of claim 22further comprising an air circulation member coupled to said firstrotatable member, said air circulation member having openings thereinfor allowing air flow therethrough.
 24. The variable speed drive ofclaim 23 wherein said rotating support is coupled to, and extends from,said air circulation member, said air circulation member comprising afan that is located adjacent to said hub second end.
 25. The variablespeed drive of claim 22 wherein the drive has a power rating and a sizeto achieve the power rating, with each of said rotating conductorshaving an outside diameter that is independent of the size of the drive.26. The variable speed drive of claim 22 wherein said electricalcouplings of said rotating conductors to said stationary conductors areinside of a housing.
 27. The variable speed drive of claim 22 whereinsaid bearing is physically separated from said rotating conductors andsaid stationary conductors.
 28. The variable speed drive of claim 22wherein said bearing further comprises a roller bearing.
 29. Thevariable speed drive of claim 22 wherein at least one of the rotatingconductors is annular.
 30. The variable speed drive of claim 29 whereinthe drive has a power rating and a size to achieve the power rating,with each of said rotating conductors having an outside diameter that isindependent of the size of the drive.
 31. The variable speed drive ofclaim 22 wherein said plural rotating conductors are located beyond saidhub second end such that said hub second end is interposed between saidrotating conductors and said hub first end.
 32. A variable speed drive,comprising:a first rotatable member that comprises alternating north andsouth poles and a drive coil; a second rotatable member that comprisesan armature; one of said first rotatable member or said second rotatablemember comprising a hub, the other of said first rotatable member orsaid second rotatable member being structured and arranged to be coupledto a load; said poles being separated from said armature by a gap; saiddrive coil located adjacent to said poles, said poles providing a pathfor a magnetic field produced by said drive coil; said hub having firstand second ends, said hub first end having an opening for receiving amotor shall, said hub being structured to rotate about an axis ofrotation, said hub having a size that is large enough for said hub firstend to receive said motor shaft; an air circulation member coupled tosaid first rotatable member so as to be adjacent to said hub second end,said air circulation member having openings therein for allowing airflow therethrough; a rotary electrical coupling located adjacent to saidhub second end, said rotary electrical coupling being structured andarranged to rotate about said axis of rotation, said rotary electricalcoupling being electrically connected to said drive coil and beingstructured and arranged to be electrically connected to an electricalsource so as to provide an electrical connection between said drive coiland said electrical source, said rotary electrical coupling having arotational portion that is coupled to said air circulation member so asto rotate with said drive coil, said rotary electrical coupling alsohaving a stationary portion that is stationary relative to said drivecoil, said rotary electrical coupling being sized independently of saidhub size.
 33. A variable speed drive, comprising:a first rotatablemember that comprises alternating north and south poles and a drivecoil; a second rotatable member that comprises an armature; one of saidfirst rotatable member or said second rotatable member comprising a hub,the other of said first rotatable member or said second rotatable memberbeing structured and arranged to be coupled to a load; said poles beingseparated from said armature by a gap; said drive coil located adjacentto said poles, said poles providing a path for a magnetic field producedby said drive coil; said hub having first and second ends, said hubfirst end having an opening for receiving a motor shaft, said hub beingstructured to rotate about an axis of rotation, said hub having a sizethat is large enough for said hub first end to receive said motor shaft;a rotating support coupled to said first rotatable member and locatedadjacent said hub second end, said rotating support being structured andarranged to rotate about said axis of rotation; plural rotatingconductors coupled to said rotating support so as to rotate therewith,said rotating conductors being electrically coupled to said drive coil;said rotating support and said rotating conductors being sizedindependently of said hub size; plural stationary conductors, each ofwhich is electrically coupled to a respective one of said rotatingconductors; a stationary support coupled to said plural stationaryconductors, said stationary support being coupled to said rotatingsupport by way of a bearing, said bearing being electrically isolatedfrom said rotating conductors and said stationary conductors; saidelectrical couplings of said rotating conductors to said stationaryconductors being located inside of an enclosed housing, said housingbeing fully supported by said hub.
 34. The variable speed drive of claim33 wherein said housing comprises a stationary component and a rotatingcomponent, said rotating component being coupled to said rotatingsupport, said rotating component and said stationary component beingcoupled together by a bearing.